An optical beam can be manipulated to obtain desired effects for various applications. One type of optical manipulation is color filtering. For example, the spectral composition of a beam can be filtered by using an optical wavelength filter to obtain light of a desired wavelength or within a certain wavelength range. Optical color filters can produce color images in display systems such as liquid crystal displays ("LCDs") in projectors, laptop computers, and camcorders.
Many conventional optical color filters operate based on absorption. Such a filter transmits light of a desired color and absorbs light of other colors. In a color LCD, three different absorbing color filters can be implemented in the three adjacent pixel cells to form one color pixel. Such filters are lossy since only about one third of a white beam is actually used for color display. This low efficiency significantly reduces the image brightness for a given light source.
Color wheels are also absorbing color filters. As the wheel spins, a white beam is intercepted and absorbed by different absorbing materials on the wheel. Thus, different colors can be obtained in the transmitted light. In addition to the above absorption loss of light, a color wheel can also be prone to mechanical failure because of tear and wear of the moving wheel.
Another common type of optical manipulation is beam steering where the direction of an optical beam is steered in a controlled manner. For example, laser vector displays and laser video projectors use beam scanners to scan laser beams at high speeds to form images. One type of beam scanners are based on a mirror or a prism engaged to a moving device such as a galvanometer. Such scanners are relatively slow due to the inertia of the galvanometer and the attached optical element. Wear and tear of the galvanometer associated with the motion of the galvanometer also adversely affect the reliability and durability of such beam scanners.
Therefore, there exists a need for efficient color filters and for reliable beam scanners without moving parts.